Field
The presently disclosed subject matter relates to a lightening apparatus having a plurality of light-emitting elements such as light-emitting diode (LED) elements and organic or inorganic electro-luminescence (EL) elements arranged in a matrix.
Description of the Related Art
Conventionally, a lightening apparatus formed by LED elements arranged in a matrix including “m” rows and “n” columns has been used as a vehicle headlamp. In such a lightening apparatus, luminous intensities of the LED elements are individually controlled to realize an adaptive drive beam (ADB) and an adaptive front-lighting system (AFS) (see: JP2013-54849A).
For driving the conventional lightening apparatus, there are two driving methods: a static driving method and a dynamic driving method.
In the static driving method, all cathode electrodes of the LED elements are commonly grounded, while there are a plurality of luminous drive voltage lines each connected to one of the LED elements. Thus, the luminous intensities of the LED elements can individually be controlled.
In the static driving method, however, a large number of voltage lines, i.e., “m×n” voltage lines are required, which would increase the lightening apparatus in size.
On the other hand, in the dynamic driving method, there are “m” reference voltage lines each connected to all the cathode electrodes of the LED elements belonging to one row, and “n” drive voltage lines each connected to the LED elements belonging to one column. That is, only a small number of voltage lines, i.e., only (m+n) voltage lines are required, which would decrease the lightening apparatus in size as compared with those of the static driving method.
In the dynamic driving method, however, since the rows of the LED elements are time-divisionally driven, when the number of rows of the LED elements is increased, the luminous period of the LED elements is decreased, which would decrease the luminous intensity.